DIXON, Ill. -- As Mitt Romney was delivering a speech centered on the theme of "economic freedom" in Chicago on Monday, Rick Santorum was about 100 miles west slamming Romney on the same thing.

"Let's just be brutally honest about it: There's one candidate in this race who can never make this race about freedom, because he simply abandoned freedom when he was governor of Massachusetts, and he abandoned it when he promoted Obamacare in 2009," Santorum said.

Santorum hit Romney for the health care overhaul he signed into law in 2006 as the governor of Massachusetts. Santorum has said it is similar to President Barack Obama's federal law in that it mandates the purchase of health insurance, and has also pointed out that Romney recommended a mandate approach as a national model.

"Obamacare is the number one issue in this race. It's an issue about fundamental freedom," Santorum said, in a speech delivered here in the boyhood hometown of former President Ronald Reagan.

Santorum stood in front of a statue of Reagan as a young man riding a horse, outside in 70-degree weather on the banks of the Rock River. A former U.S. Senator from Pennsylvania, Santorum has made Romney's health law a central component of his attacks on the frontrunner.

In Romney's speech Monday, he went down a long list of things that he said constitute an "assault on our economic freedom" by the Obama administration. Notably missing from his list of Obama policies constraining freedom: the health care law. Romney did say during a question and answer session that he would seek to repeal the law, but his decision to leave the issue out of his prepared remarks looked as if he were avoiding it.

"In speeches he never talks about it. He can't talk about it," Santorum taunted. "Why would the Republican party put up a nominee who takes that issue off the table?"

UPDATE: 4:06 p.m. -- In an email to The Huffington Post, a Romney spokeswoman said that "Senator Santorum’s false and flailing attacks can’t obscure the fact that he is an economic lightweight who was roundly rejected by own constituents six years ago. Someone who was part of the problem can’t be part of the solution.”

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